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diy solar

GUIDE to properly Top-Balance and Charge a LFP Battery: Part 1

Yeah, but shvm is an engineer with a degree!??

It's a perfect example of education/experience/competence in one area making one believe they have inherent competence in other areas.

I too have an engineering degree and 30 years of engineering experience in a technical field, and aside from learning V = I * R and P = I * V, it didn't grant me ANY competence with batteries.

However, a few thousand hours of working with literally 10s of thousands of battery modules of multiple chemistries over the last eight year has bestowed something above a "layman's" level of expertise. I still have a lot to learn. Just not from @shvm until he/she/they/it demonstrates some level of competence.

Oh, and @Partimewages, you should be more selective on who you follow over at Community... :p
 
This thread is starting to remind me of a story I once heard on the Art Bell show (a late night radio show on paranormal topics), called "Mel's Hole". It was about a hole in the ground of his family property in Washington state that was mysterious to them. Anything they dropped into the hole, a dead cow, a dead car, garbage, etc, would never make a single sound. No crash or bang. They stopped trying to measure the depth at about 80,000 feet (24000m)?! They lowered a bucket of ice cubes deep into the hole, left it there for a few hours, then pulled it up. The ice cubes were still frozen solid but now were hot to the touch. Rumors it was a hole built by aliens they used to go into inner earth and all that It got weirder, too, especially when he did Part 2 a couple years later. Really weird.

Finally, after what must've been over 4 hours of this story on the radio, the guy, Mel, finally let's out that the reason he had to move from Washington state, was the feds were after him. "Oh so why where they after you?" Art Bell asked. He said they wanted what he was growing in his greenhouse and put in him their special ops program but he didn't want to work for them (or that's my memory of it anyways). Long story short, it took still a bit longer for Art Bell to finally suss it out of Mel...Mel was growing psilocybin mushrooms in his greenhouse near the hole!

"AHhhhhhhhhhhhhh......." said Art. "You've got to be kidding me! You've been growing mushrooms???"

@sunshine_eggo tagged since you seem to like weird shit, lol.


If you want to listen to the original episode (there are two more even weirder), here's the link:
https://www.coasttocoastam.com/videos/art-bell-vault/guest-only-mel-of-mel-s-hole/ (you need to pay to listen, $7/mo)

Despite the fact that "Mel" never existed in the area he claims to have lived and he was likely in la-la land of shrooms, it was hands down one of the single most entertaining stories I have ever heard in my life!
 
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I have no degree of any sort. Ate slept and drank electronics for my last two years of vocational school. The last 40 years have been spent in the electrical/DDC/HVAC industry. Throughout that time I've seen a lot.
I can usually spot BS from a mile away including those that have everything figured out.
I'm still however a student!
 
Late night with Art Bell!

I used to LOVE that show, especially since I was a night owl in that time of life. So many crazy stories I got to hear. Hearing of Dr Greer and watching his The Disclosure Project was eye-opening...lots of ex high-level military (or a good hoax) who shared their knowledge of aliens and UFO's was the pinnacle of it (along with Mel's Hole).

Eventually I grew tired of the occult and paranormal stuff, it gave me an ongoing sense of paranoia. Over things of which I have no control, if true. I've found other interests now, like LFP and camping for weeks off-grid in our trailer!
 
ME = "Hey whatever most of us are doing seems to work - there's no fire -- good enough for me"

Self-appointed "LFP Expert" - OMG your using a 2/0 instead of 3/0, your torqueing your batteries at 8 n/m not 8.5, your charging them to 3.65 instead of 3.6255, you did not compress your batteries - you did not grind the terminal base down to a shining marble finish before connecting busbar, YOU realize that you have taken at least 2 days off the lifespan of a 15 year battery!!!"

Haha, yeah totally, I just try to follow all these guidelines (except for springs, just tighten bolts) and crossing my fingers, hoping I can add a couple extra bonus days to my battery lifespan (before all the new battery tech hits the market and obsoletes LFP). I hope I didn't lose too many cycles for not using springs and just tightening my cell clamps with my trusted arm-wrench and no torque wrench..

Hey, this is a good place for a stickup (might as well add it to the mix):
 
:ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO:

View attachment 180837

yea.. right... nuff said... I'm joining @42OhmsPA with his ? again...

Seagal,
Shvm's background got clipped:
Masters in Industrial & Manufacturing Engineering
 
Thank you for putting efforts to read what I wrote.

I understand that you mean voltage levels like 12 or 48 volts,
You and I both know that nominal voltage of LFP is 3.2 or 3.22 voltage. You understand that I'm talking about 12/24/48 V systems still you chose to nitpick.
but you're the one coming here an insisting you're are the smartest person in the room and that everyone else is an idiot.
You're cooking things up at this point trying to be demeaning.

Have you tested a cell? Do you know what this newly invented "fully charged resting voltage" might be?
My emphasis is that anyone can determine this voltage by experimenting if they don't trust me. This is well known to be ~3.37 V for LFP.

Underline is my added emphasis. That's not the resting voltage.
Nice try but you missed the 'less than' '<' mark to the left of 3.65V. Resting voltage is lesser than 3.65 V.
3.37 V < 3.65 V.
Voltage isn't a good indicator that the cell is charged and unless you've done lots of research, on your cell voltage curve, it would be much easier to use coulomb counting/SOC to know when to restart a charge cycle.
You are ignoring the what I term continuity aspect of Solar applications.
If a cell is fully charged at say, afternoon, and there is excess power available, the cell can't accept more charge.
Now suppose, if demand comes and the excess power can't meet the load, then power must be drawn from the cell.

Now if that demand is completed (no need to discharge from cell) and excess energy is there, then the OCV of the Cell has to be below FCV.
Voltage in the absence of current is a good indicator of when to initiate top-up charging cycle again.
Honestly, I feel like you left out part of the math here. I expected a formula to say to charge at 0.011c to x.xx volts.
I knew this would come up.

The last edit to that post was in November. Your concerns are addressed.

I don't feel the need to bog down everyone with math where it is unnecessary.
 
a few thousand hours of working with literally 10s of thousands of battery modules of multiple chemistries over the last eight year has bestowed something above a "layman's" level of expertise. I still have a lot to learn.

If the underlying foundation of your very understanding is at fault, there is only so much difference those 'thousands of hours' and experience can make.

I can smell from miles away who is confrontational possessing a good understanding and who isn't.

This you??

Balancing above 3.40 is productive. Cells in near perfect balance at 3.45V nearly always extrapolate to near perfect balance at 3.65V.

From how I understand things, (Top) - balancing basically implies bringing cells to 100% SOC. It's not some beauty pageant of aligning voltages.
The resting OCV of a LFP Cell at 100% SOC is 3.37 V
I can't understand nor do I want to know whatever you are doing above 3.37V regarding balancing.

Want more?

Fast charging to full: 3.55-3.65V/cell - 30 minute absorption time.
Slow charging/longer cycle life (98%+ charge): 3.45V/cell - 4+ hour absorption time.
Float (95%+): 3.4V/cell
This is you talking of floating LFP above 3.4/Cell when 3.37 Volts is the voltage corresponding to 100% SOC.

'absorption time', 'slow charging', 'longer cycle life' - hot damn !!

It is you who needs to get down your high horse.
The reason you were ignored because your criticism is hollow. Engaging with you will derail any chance of meaningful discussion happening.
 
Despite all the theories, papers and forum posts read over many years our battery has never required balancing since the original careful top balance.

In the meantime we will continue to use our 9 year old 300Ah 4 cell Sinopoly LiFePO4 battery to both power the house and start our motorhome 3.9l turbo diesel Fuso Canter truck engine often multiple times daily during our full-time travels.

I occasionally check the cell balances and practice a little tweaking, but apart from any phycological satisfaction it achieves absolutely nothing. It certainly can have no effect on battery capacity.
Pulling any 100mV deviant cell into line requires no more than a few seconds and mWh at 30A.

No standard BMS unit or balancing involved here. The 740A peak engine start current would be tricky.
14.1V maximum from any charge source, 20% SOC alarm and 12.5V Victron BatteryProtect disconnect. Never triggered.

With just a 5% capacity loss over 9 years at the last November annual C/10 test we must be doing something right despite all the doomsayers.
A recent push to 14.5V from our 14.1V always 100% SOC took less than 30 seconds at 30A.
"Float" is 13.40V but that is never maintained for long. We use our battery.


Click to enlarge.
This is the way.
 
From how I understand things, (Top) - balancing basically implies bringing cells to 100% SOC. It's not some beauty pageant of aligning voltages.
The resting OCV of a LFP Cell at 100% SOC is 3.37 V
I can't understand nor do I want to know whatever you are doing above 3.37V regarding balancing.

Top balancing necessarily requires charging, so resting voltage is irrelevant. If you try to balance a resting pack, it turns into a game of whack-a-mole as you bring cells from resting to charging state.

A charging cell is not 100% SOC at 3.37V. It's still in the knee of the curve. You need all the cells to be in a charging state over 3.4V to ensure that they're near 100% SOC. You're out of the knee of the curve, and voltage actually means something at that point.

IMO, you don't need to go over 3.45V or so, but the magic 3.4V (ish) line is hard to argue against when top balancing.
 
Top balancing necessarily requires charging, so resting voltage is irrelevant. If you try to balance a resting pack, it turns into a game of whack-a-mole as you bring cells from resting to charging state.

A charging cell is not 100% SOC at 3.37V. It's still in the knee of the curve. You need all the cells to be in a charging state over 3.4V to ensure that they're near 100% SOC. You're out of the knee of the curve, and voltage actually means something at that point.

IMO, you don't need to go over 3.45V or so, but the magic 3.4V (ish) line is hard to argue against when top balancing.

Pray, tell me one simple thing:

If I take N number of factory new Cells, charge each one of them individually to 100% SOC and then connect them in series,

Will the resulting battery considered to be top Balanced or not?

Answer with just YES or NO.

If you answered in yes, Congrats, you just contradicted your own first statement of your reply.

Where is everyone learning things like this from? Is there a top balancing research written by any LFP engineer or is it just 'experience' ??
 
Pray, tell me one simple thing:

If I take N number of factory new Cells, charge each one of them individually to 100% SOC and then connect them in series,

Will the resulting battery considered to be top Balanced or not?

Answer with just YES or NO.

Insufficient information to answer with only yes or no.

If you did it INDIVIDUALLY and SIMULTANEOUSLY, the answer is yes. That's how I did it, but I have the ability to charge multiple cells simultaneously.

If you did it INDIVIDUALLY and SEQUENTIALLY with the same charger, then the answer is no.
 
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